Qemu is a generic open source processor and system emulator. It achieves good performance from using a Just-in-time compilation.
- 1 Processor
- 2 System architecture
- 3 MIPS pseudo board
- 4 Status
- 5 Common Problems
- 6 MIPS HOST SUPPORT
- 7 See also
- 8 Credits
$ qemu-system-mips64 -cpu '?' MIPS '4Kc' MIPS '4KEcR1' MIPS '4KEc' MIPS '24Kc' MIPS '24Kf' MIPS 'R4000' MIPS '5Kc' MIPS '5Kf' MIPS '20Kc'
All processor emulations claim to have primary caches however the cache effects are not simulated and cacheops are treated as noops. This is a design decision to improve performance over accuracy. No benchmarking has been done however it is expected that the performance of the virtual MIPS system will be comparable to emulation of the other processors.
$ qemu-system-mips -M ? Supported machines are: mips mips r4k platform (default) malta MIPS Malta Core LV pica61 Acer Pica 61 mipssim MIPS MIPSsim platform
The Qemu distribution does not contain any firmware for MIPS. This is only a minor problem as unlike on a real system Qemu's virtual hardware is mostly initialized after a reset.
There is also a mmon port to the Qemu.
MIPS pseudo board
This paragraph describes the architecture of the MIPS system (mips) that currently is being emulated by Qemu. As Qemu is still very much work in progress this is expected to change.
Qemu emulates a simple machine with ISA-like bus. ISA IO space mapped to the 0x14000000 (PHYS) and ISA memory at the 0x10000000 (PHYS, 16Mb in size). All peripherial devices are attached to this "bus" with the standard PC ISA addresses.
Qemu is emulating the standard builtin interrrupt controller including soft interrupts and the count/compare interrupt of R4000-class processors. Cascaded externally to that is a i8259 PIC interrupt controller that is cascaded to the CPU's INT0.
Qemu is emulating a standard VGA graphics card however underlined, bold and blinking attributes are not supported.
Qemu is emulating a PC-style 8250-based serial interface.
Qemu is emulating a single ISA NE2000 network card.
Qemu emulates a generic PC-style IDE interface.
Qemu supports other peripherals however support for them has not been integrated or tested into the MIPS port.
At this time the MIPS support still is in alpha stage. There is not much firmware for Qemu yet, so Qemu does the basic initialization as well as loading kernel and ramdisk itself. The Linux kernel has a special configuration to support the Qemu platform, no additional patches are needed.
A guide for installing Debian can be found here.
MIPS BIOS not found on startup
[ralf@box qemu]$ qemu-system-mips -kernel /tftboot/192.168.0.1/vmlinux.bin -m 16 -nographic (qemu) mips_r4k_init: start mips_r4k_init: load BIOS '/usr/local/share/qemu/mips_bios.bin' size 131072 qemu: could not load MIPS bios '/usr/local/share/qemu/mips_bios.bin' [ralf@box qemu]$
There currently is no MIPS BIOS file for Qemu (see firmware). However if passed a -kernel argument qemu will not call the firmware at all, so this does no harm at all. Therefore, a command such as
dd if=/dev/zero of=/usr/local/share/qemu/mips_bios.bin bs=1024 count=128
will generate a firmware file that will do the job for now.
Since Qemu 0.8.1 this workaround is obsolete, a missing BIOS file triggers only a warning message.
MIPS HOST SUPPORT
In 2004, I successfully compiled QEMU on a SGI machine, using a patch found here:
I hope this patch could merge into the new qemu release. Thanks! -- Tinybit <tinybit at tom dot com>
Originally authored by French wizzard Fabrice Bellard, Jocelyn Mayer did add support for MIPS as a target, others are now trying to complete the project.